Description: Microscopic. A single cell of irregular in shape and colourless hairs. Forms patches in the host.

Habitat: Very rare. Endophytic in other algae including: Laminaria, Ulva, Entreromorpha and Dumontia. Littoral and sublittoral.

Distribution: Rarely recorded from the British Isles. Europe: Southern North Sea and Norway. Atlantic coast of North America: Canada and Massachusetts. Further afield: the Canary Islands and Japan.

Distribution Map from NBN: Blastophysa rhizopus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Blastophysa rhizopus at iNaturalist World Species Observations database.

WoRMS: Blastophysa rhizopus at World Register of Marine Species.